From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B621FC48297 for ; Fri, 9 Feb 2024 08:15:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To: Subject:MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=t05FIJR87SmlAMR8pTw95L9JcK0G7NagG7mmHH9I0E8=; b=eiUaOwf4PEQfNU NF43MP14pSnh58csIh1zdAStsAR53VuvqemKtNk7Gcv06ywB+zsAZkP9/HLCtUKQVST1nPL/27oj4 T2nvD8fkffbmy2JK0Zmr5jReg6fa0zhTk4/WV13P+uMYrvkF4m1qrd/aWRwlzgBv2yNIDWSezKLLw 43Ok392AJVCx8N6FFR134dZpSXzliKlfbBWCQf7vuSHbhLTAvuw4zpMYQlNwuUsIQUOMwu4Oo5h5Q 34LoS0R2GP9Hh9Gk2DMK6fAl4123L5DUF77xl3D0CXAOKsjXvUs3asN5HWX7scWiV0WjR9RL4M6hE jCpFT8rhrkZazdVrRi5w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rYM2C-0000000GQYs-37Nb; Fri, 09 Feb 2024 08:14:56 +0000 Received: from mgamail.intel.com ([198.175.65.10]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rYM2A-0000000GQYA-3VGh for linux-arm-kernel@lists.infradead.org; Fri, 09 Feb 2024 08:14:56 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1707466495; x=1739002495; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=odqYYfgwkzr9LdQp9Op8mRYllrVCWTdsitkPlh2e2hM=; b=RW8Rm8j6IEcrZapXzOKQ8ni1GXO80wkjzKOacsD859KINJzm4ALvWLN6 R4IECHXJXiCMjXiHzMoAphl1tYtbEu6o6a0yBznkch6bX88DBbLkiPhql TrrU7T6aGq0R2RFn1pxyMgDcEoqU3pMp8Y3de8k9hYcTOG6atkBMzwuMW t5++JIbGdg+tc89M3v8ZQBkNPt75VAxAj8+DrWfoSbjjR8sqslHv+f5+u CzRRvAAj4jHDN7yfL3nt693SOKq8RzxMphy5pNQe5WFMwlHvAoGXiGO6J b68zx8wjth78OdIhr2zW66BE9+Q99a8NQm80QMAkLakRbnkoAQFmFVCGC g==; X-IronPort-AV: E=McAfee;i="6600,9927,10978"; a="18804149" X-IronPort-AV: E=Sophos;i="6.05,256,1701158400"; d="scan'208";a="18804149" Received: from orviesa009.jf.intel.com ([10.64.159.149]) by orvoesa102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Feb 2024 00:14:54 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.05,256,1701158400"; d="scan'208";a="1889450" Received: from ahunter6-mobl1.ger.corp.intel.com (HELO [10.0.2.15]) ([10.252.61.190]) by orviesa009-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Feb 2024 00:14:48 -0800 Message-ID: Date: Fri, 9 Feb 2024 10:14:44 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V5 01/12] perf/core: Add aux_pause, aux_resume, aux_start_paused To: Andi Kleen Cc: Peter Zijlstra , Ingo Molnar , Mark Rutland , Alexander Shishkin , Heiko Carstens , Thomas Richter , Hendrik Brueckner , Suzuki K Poulose , Mike Leach , James Clark , coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, Yicong Yang , Jonathan Cameron , Will Deacon , Arnaldo Carvalho de Melo , Jiri Olsa , Namhyung Kim , Ian Rogers , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org References: <20240208113127.22216-1-adrian.hunter@intel.com> <20240208113127.22216-2-adrian.hunter@intel.com> Content-Language: en-US From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240209_001454_941343_3771C44A X-CRM114-Status: GOOD ( 13.49 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 9/02/24 02:13, Andi Kleen wrote: >> +static void __perf_event_aux_pause(struct perf_event *event, bool pause) >> +{ >> + if (pause) { >> + if (!READ_ONCE(event->aux_paused)) { >> + WRITE_ONCE(event->aux_paused, 1); >> + event->pmu->stop(event, PERF_EF_PAUSE); >> + } >> + } else { >> + if (READ_ONCE(event->aux_paused)) { >> + WRITE_ONCE(event->aux_paused, 0); >> + event->pmu->start(event, PERF_EF_RESUME); >> + } > > This doesn't look atomic. Either the READ/WRITE once are not needed, > or you need an actually atomic construct. Yes READ_ONCE / WRITE_ONCE is not really needed here. > >> + >> + rb = ring_buffer_get(event); >> + if (!rb) >> + return; >> + >> + local_irq_save(flags); >> + /* Guard against NMI, NMI loses here */ >> + if (READ_ONCE(rb->aux_in_pause_resume)) >> + goto out_restore; >> + WRITE_ONCE(rb->aux_in_pause_resume, 1); > > >> + barrier(); >> + __perf_event_aux_pause(event, pause); >> + barrier(); >> + WRITE_ONCE(rb->aux_in_pause_resume, 0); > > Dito. > The writes to rb->aux_in_pause_resume must be done only once. It might be possible to get away without WRITE_ONCE(), but really the compiler should be informed not to make assumptions. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel